Some cameras with such functions as automatic exposure control and auto focusing are provided with a shutter release button which can press by two stages as halfway pressing and full pressing in order to shorten a time lag between a shutter release operation and an actual shutter release. During the halfway pressing, preparatory operations for shooting are carried out, including photometry, aperture control, auto focusing and focus-locking. Upon full pressing of the shutter release button, the actual shutter release is executed.
With such a shutter release button as having the two stages, it is difficult to apply force appropriately to press the button from the half-pressed position to the full-pressed position, which often causes hand shaking or wrong operation. On the other hand, when the shutter release button is moved from the half-pressed position to the full-pressed position in such a short time that the camera cannot complete the exposure control and auto focusing before the shutter release button reaches the full-pressed position, so a time lag from the shutter release operation to an actual exposure operation becomes longer, missing a right moment for the exposure. In order to minimize the time lag during the shutter release operation, it is known to provide a camera with a touch sensor detecting that fingers of a camera operator touch the shutter release button, or an infrared radiation sensor detecting that the fingers come close to the shutter release button, for example, from Japanese Laid-open Patent Application Nos. 2003-287799, 2003-280076 and 2004-7221.
However, since the shutter release button is ordinary located in a position where the camera operator can easily put the fingers on it while holding or framing the camera, the camera operator may often put the fingers close to the shutter release button without intending to capture an image while carrying the camera about. If the preparatory operations for shooting are carried out every time the fingers touch or get close to the shutter release button, a power source battery of the camera would be uselessly consumed.